| Message ID | d12a15f496ca472e100798ac2cd256fbfc1de15d.1583952276.git.amanharitsh123@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Handled return value of platform_get_irq correctly | expand |
On Wed, Mar 11, 2020 at 8:19 PM Aman Sharma <amanharitsh123@gmail.com> wrote: > Signed-off-by: Aman Sharma <amanharitsh123@gmail.com> > --- > drivers/pci/controller/pci-v3-semi.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/controller/pci-v3-semi.c b/drivers/pci/controller/pci-v3-semi.c > index bd05221f5a22..a5bf945d2eda 100644 > --- a/drivers/pci/controller/pci-v3-semi.c > +++ b/drivers/pci/controller/pci-v3-semi.c > @@ -777,9 +777,9 @@ static int v3_pci_probe(struct platform_device *pdev) > > /* Get and request error IRQ resource */ > irq = platform_get_irq(pdev, 0); > - if (irq <= 0) { > + if (irq < 0) { Have you considered: https://lwn.net/Articles/470820/ TL;DR Linus (both of them) are not with you on this. And that is why the code is written like this. Do you really have a platform that could return 0 as IRQ here? In that case, can we fix it? > dev_err(dev, "unable to obtain PCIv3 error IRQ\n"); > - return -ENODEV; > + return irq; That's OK with me. Yours, Linus Walleij
[+cc Marc, Thomas] Hi Linus, On Thu, Mar 12, 2020 at 03:07:58PM +0100, Linus Walleij wrote: > On Wed, Mar 11, 2020 at 8:19 PM Aman Sharma <amanharitsh123@gmail.com> wrote: > > Signed-off-by: Aman Sharma <amanharitsh123@gmail.com> > > --- > > drivers/pci/controller/pci-v3-semi.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/pci/controller/pci-v3-semi.c b/drivers/pci/controller/pci-v3-semi.c > > index bd05221f5a22..a5bf945d2eda 100644 > > --- a/drivers/pci/controller/pci-v3-semi.c > > +++ b/drivers/pci/controller/pci-v3-semi.c > > @@ -777,9 +777,9 @@ static int v3_pci_probe(struct platform_device *pdev) > > > > /* Get and request error IRQ resource */ > > irq = platform_get_irq(pdev, 0); > > - if (irq <= 0) { > > + if (irq < 0) { > > Have you considered: > https://lwn.net/Articles/470820/ > > TL;DR Linus (both of them) are not with you on this. > > And that is why the code is written like this. I'm not sure I understand you here, so please correct me when I go in the weeds. I guess you're saying that platform_get_irq() can return 0 here and we should treat that as an error? This particular driver seems to be ARM-specific -- does that mean we need to check for 0 on some arches but not others? That would definitely be suboptimal, and that's what I'd like to fix here. IIUC, in the link you mentioned, Linus T says that "dev->irq == 0" means we don't have a valid IRQ. I think that makes sense, but I'm not sure it follows that 0 must be a sensical return value for platform_get_irq(). It seems to me that platform_get_irq() ought to return either a valid IRQ or an error, and the convention for errors is a negative errno. In fact, the platform_get_irq() function comment says it returns "IRQ number on success, negative error number on failure." If we need to interpret 0 as an error on some arches, it sounds like something is wrong in the arch-specific bowels of platform_get_irq(). If platform_get_irq() returns an error, a driver might want to continue in polled mode without IRQs, in which case it could set its "dev->irq = 0" to indicate that it has no valid IRQ. But I think we might be able to separate that "stored IRQ" situation from the platform_get_irq() interface. Bjorn
On Thu, Mar 12, 2020 at 8:02 PM Bjorn Helgaas <helgaas@kernel.org> wrote: > IIUC, in the link you mentioned, Linus T says that "dev->irq == 0" > means we don't have a valid IRQ. I think that makes sense, but I'm > not sure it follows that 0 must be a sensical return value for > platform_get_irq(). It seems to me that platform_get_irq() ought to > return either a valid IRQ or an error, and the convention for errors > is a negative errno. OK I see your point. I would be fine of the code is changed from: if (irq <= 0) error; To: if (irq < 0) error retrieving IRQ if (!irq) error driver requires a valid IRQ To the driver (this one in specific) the IRQ is expected and necessary and I think it holds for most PCI hosts. Yours, Linus Walleij
diff --git a/drivers/pci/controller/pci-v3-semi.c b/drivers/pci/controller/pci-v3-semi.c index bd05221f5a22..a5bf945d2eda 100644 --- a/drivers/pci/controller/pci-v3-semi.c +++ b/drivers/pci/controller/pci-v3-semi.c @@ -777,9 +777,9 @@ static int v3_pci_probe(struct platform_device *pdev) /* Get and request error IRQ resource */ irq = platform_get_irq(pdev, 0); - if (irq <= 0) { + if (irq < 0) { dev_err(dev, "unable to obtain PCIv3 error IRQ\n"); - return -ENODEV; + return irq; } ret = devm_request_irq(dev, irq, v3_irq, 0, "PCIv3 error", v3);
Signed-off-by: Aman Sharma <amanharitsh123@gmail.com> --- drivers/pci/controller/pci-v3-semi.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)